First of all, waterskiing, wakeboarding and barefoot waterskiing all require a certain amount of fitness. You will be holding on to the rope in order to keep yourself upright and to stay behind the boat. This of course requires a lot of ab strength and is partly responsible for the ripped abs and six packs you often associate with those who participate in watersports. At the same time though the balance required to stay upright and to steer with the legs and arms is also considerable and this will further train the core muscle. In particular the motion of twisting your legs and upper body to weave around across the top of the water will develop your obliques which are the muscles that make the serrations down the side of your stomach on either side of your abs. These are very difficult to train in any other way but will make a big different to your overall physique and certainly make your mid section appear a lot more ‘cut’ and defined.